This invention relates to a magnetic disk drive.
As well known, a magnetic disk drive is a device for carrying out data recording and reproducing operations to and from a flexible disk called a magnetic disk. In recent years, magnetic disks shaving an increased capacity have been developed. A typical magnetic disk has a storage capacity on the order between 1 Mbyte and 2 Mbyte (hereinafter called a normal capacity). In contrast, a magnetic disk having a storage capacity as large as 128 Mbyte (hereinafter called a large capacity) has already been developed. Following such remarkable increase in capacity of the magnetic disk, development has also been made of a magnetic disk drive for carrying out data recording and reproducing operations to and from the magnetic disk of the large capacity type.
In the following description, a magnetic disk drive capable of carrying out data recording and reproducing operations to and from the large-capacity magnetic disk alone will be referred to as a high-density dedicated magnetic disk drive. On the other hand, a magnetic disk drive capable of carrying out data recording and reproducing operations to and from the normal-capacity magnetic disk alone will be called a normal-density dedicated magnetic disk drive. A magnetic disk drive capable of carrying out data recording and reproducing operations to and from both the large-capacity and the normal-capacity magnetic disks will be called a high-density/normal-density magnetic disk drive. The high-density dedicated magnetic disk drive and the high-density/normal-density magnetic disk drive may collectively be called a high-density magnetic disk drive.
The normal-density dedicated magnetic disk drive and the high-density magnetic disk drive are different in mechanism from each other. One of the major differences resides in a carriage drive source for driving a carriage holding a magnetic head. The carriage drive source is for moving the carriage with respect to the magnetic disk inserted in the magnetic disk drive in a predetermined radial direction of the magnetic disk. Specifically, the normal-density dedicated magnetic disk drive uses a stepping motor as the carriage drive source. The stepping motor has a rotation shaft with a lead screw. On the other hand, the high-density magnetic disk drive uses a linear motor such as a voice coil motor (VCM) as the carriage drive source.
Now, description will be made in detail as regards the voice coil motor used as the carriage drive source in the high-density magnetic disk drive. The voice coil motor is arranged at a rear side of the carriage. The voice coil motor comprises a pair of voice coils located at both sides of the carriage and a pair of magnetic circuits for producing magnetic fields in a direction intersecting electric currents flowing through the voice coils. Each voice coil is wound around a drive shaft extending in parallel to the predetermined radial direction of the magnetic disk and is movable along the drive shaft. When the electric current is made to flow through each of the voice coils in a direction intersecting the magnetic field produced by the magnetic circuit, drive force is generated in the voice coil in an extending direction of the drive shaft as a result of interaction between the electric current and the magnetic field. By the drive force, the voice coil motor makes the carriage move in the predetermined radial direction.
In the meanwhile, it is sometimes desired to transport the magnetic disk drive to another place. In this case, the carriage must be locked in order to prevent the carriage from being dislocated even if the magnetic disk drive is shaken during transportation. In the normal-density dedicated magnetic disk drive using the stepping motor as the carriage drive source, the lead screw of the stepping motor advantageously serves as a carriage locking mechanism. On the other hand, in the high-density magnetic disk drive, the carriage is freely movable in the predetermined radial direction because the linear motor such as the voice coil motor is used as the carriage drive source. Thus, in the high-density magnetic disk drive, the carriage is often dislocated due to the shaking movement during transportation and undesirably collides against other components at starting ends or terminating ends of the drive shafts.
In order to avoid the dislocation and the collision of the carriage, it is a general approach to insert a dummy diskette (magnetic disk) into the high-density flexible disk drive when it is transported. In this manner, the carriage is prevented from being dislocated even if the high-density magnetic disk drive is shaken during transportation.
In the above-mentioned approach, however, it is troublesome to manually insert the dummy diskette into the high-density magnetic disk drive every time it is transported. Sometimes, the dummy diskette is inadvertently not properly inserted into the high-density magnetic disk drive. In this event, the carriage can be freely dislocated when the high-density magnetic disk drive is shaken during transportation.